Evaluation of the Reconstruction Parameters of Brain Dopamine Transporter SPECT Images Obtained by a Fan Beam Collimator: A Comparison with Parallel-hole Collimators

Objective(s): The purpose of this study was to examine the optimal reconstructionparameters for brain dopamine transporter SPECT images obtained with a fanbeam collimator and compare the results with those obtained by using parallel-holecollimators.Methods: Data acquisition was performed using two SPECT/CT devices, namely aSymbia T6 and an Infinia Hawkeye 4 (device A and B) equipped with fan-beam(camera A-1 and B-1), low- and medium-energy general-purpose (camera A-2 andB-2), and low-energy high-resolution (camera A-3 and B-3) collimators. The SPECTimages were reconstructed using filtered back projection (FBP) with Chang’sattenuation correction. However, the scatter correction was not performed. A poolphantom and a three-dimensional (3D) brain phantom were filled with 123I solution toexamine the reconstruction parameters. The optimal attenuation coefficient wasbased on the visual assessment of the profile curve, coefficient of variation (CV) [%],and summed difference from the reference activity of the pool phantom. The optimalButterworth filter for the 3D-brain phantom was also determined based on a visualassessment. The anthropomorphic striatal phantom was filled with 123I solution atstriatum-to-background radioactivity ratios of 8, 6, 4, and 3. The specific binding ratio(SBR) of the striatum (calculated by the CT method) was used to compare the resultswith those of the parallel-hole collimators.Results: The optimal attenuation coefficients were 0.09, 0.11, 0.05, 0.05, 0.11, and, 0.10cm-1 for cameras A-1, A-2, A-3, B-1, B-2, and B-3, respectively. The cutoff frequencies ofthe Butterworth filter were 0.32, 0.40, and 0.36 cycles/cm for camera A, and 0.46, 0.44,and 0.44 cycles/cm for camera B, respectively. The recovery rates of the SBRmean withcamera A were 51.2%, 49.4%, and 45.6%, respectively. The difference was notstatistically significant. The recovery rates of the SBR with camera B were 59.2%,50.7%, and 50.8%, respectively. Camera B-1 showed significantly high SBR values.Conclusion: As the findings indicated, the optimal reconstruction parameters differedaccording to the devices and collimators. The fan beam collimator was found toprovide promising results with each device